Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$77.85	7.389%	$83.6023	$83.60	$83.60	$83.60
Purchase #2	$53.53	6.701%	$57.117	$57.12	$57.10	$57.10
Purchase #3	$80.67	6.183%	$85.6578	$85.66	$85.65	$85.70
Purchase #4	$10.72	13.523%	$12.1697	$12.17	$12.15	$12.20
Purchase #5	$196.74	11.644%	$219.6484	$219.65	$219.65	$219.60
Purchase #6	$221.34	5.470%	$233.4473	$233.45	$233.45	$233.40
Purchase #7	$224.44	10.707%	$248.4708	$248.47	$248.45	$248.50
7 purchase totals =	$865.29		$940.1133	$940.12	$940.05	$940.10